Quinacridone colorant

Classification Quinacridone colorant Empirical C22H16N2O2 Properties M.w. 340.38... 

CAS 1047-16-1 EINECS/ELINCS 213-879-2 Synonyms Cl 46500 5,12-Dihydroquino [2,3-b] acridine-7,14-dione Pigment red 122 Quinacridone Quinacridone red Quinacridone violet Quino (2,3-b) acridine-7,14-dione, 5,12-dihydro-Classification Quinacridone colorant Empirical C20H12N2O2... 

Practical methods for synthesis and elucidation of the optimum physical forms were developed at Du Pont (13). The violets fill the void in the color gamut when the inorganics are inadequate. The quinacridones may be used in most resins except polymers such as nylon-6,6, polystyrene, and ABS. They are stable up to 275°C and show excellent weatherabiUty. One use is to shade phthalocyanines to match Indanthrone Blue. In carpeting, the quinacridones are recommended for polypropylene, acrylonitrile, polyester, and nylon-6 filaments. Predispersions in plastici2ers ate used in thermoset polyesters, urethanes, and epoxy resins (14). 

Fluorescent small molecules are used as dopants in either electron- or hole-transporting binders. These emitters are selected for their high photoluminescent quantum efficiency and for the color of their emission. Typical examples include perylene and its derivatives 44], quinacridones [45, penlaphenylcyclopenlcne [46], dicyanomethylene pyrans [47, 48], and rubrene [3(3, 49]. The emissive dopant is chosen to have a lower excited state energy than the host, such that if an exciton forms on a host molecule it will spontaneously transfer to the dopant. Relatively small concentrations of dopant are used, typically in the order of 1%, in order to avoid concentration quenching of their luminescence. 

The synthesis of linear turns-quinacridone (2.38) was reported in 1935 by Liebermann [26] and was cursorily looked at as a red vat colorant but not developed commercially. It was more than twenty years later that the DuPont company introduced these compounds as pigments under the trade name of Cinquasia. Their chemical structures are based on Cl Pigment Violet 19 (2.38). As with the phthalocyanines, this compound can exist in several polymorphic forms in this case there are three, termed a-, p- and y- forms only the last two being useful as pigments. The first three pigments were called Cinquasia Red B (y-form, size above 1000 nm), Cinquasia Red Y (y-form, size below 1000 nm) and Cinquasia Violet R (P-form). 

Particularly large color changes are associated with the transition from solution to solid state in heterocycles such as the cross-conjugated indigo system or the quinacridone skeleton. Quinacridone pigments, dissolved in concentrated sulfuric acid or in DMF, exhibit a pale yellow shade the intense red color appears only in the solid state. This is a particularly distinctive example to demonstrate the correlation between crystal lattice interactions and hue [9]. 

The thermal requirements for pigments which are targeted for PETP melt extrusion are particularly severe. However, it is important to consider the individual conditions at the various stages of polymer coloration. Pigments, for instance, which are added during the so-called condensation process in a glycol dispersion prior to transesterification or condensation in the autoclave, are exposed to temperatures between 240 and 290°C for 5 to 6 hours [43]. These harsh conditions are only tolerated by very few polycyclic pigments, primarily by representatives of the quinacridone, copper phthalocyanine, naphthalenetetracarboxylic acid, and pery-lene tetracarboxylic acid series. 

A few years ago the pigment was withdrawn from the market. P.R.212 was rarely sold outside Japan. It produces considerably bluish shades of red, which might be considered pink. Compared to the similarly colored quinacridone pigment P.R.122, P.R.212 is duller, weaker, and less fast. 1/3 SD letterpress proof prints, for instance, equal step 2-3 on the Blue Scale for lightfastness while prints containing P.R.122 equal step 6-7. P.R.212 is also less lightfast than the somewhat more bluish and duller benzimidazolone pigment P.V.32, a coloristically related maroon the difference is 2 to 3 steps on the Blue Scale. 

All industrially significant quinacridone pigments are deeply colored products. They cover the spectral range from yellowish red to violet shades. Quinacridone pigments do not melt but decompose at high temperature. 

The polycyclic colorants which are discussed in this context (and this is also true for copper phthalocyanine and quinacridone pigments) as a rule evolve from the manufacturing process as products with relatively coarse particles, which is in contrast to azo pigments (Sec. 2.2.3). 

Similarly, 6,13-dihydroquinacridone is virtually colorless, whereas quinacridone is a colored pigment. Generally, the longer the conjugated system the longer the wavelength of the absorbed visible light. 

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